Although numerous regional variations exist, most of Ydra follows a system of social classes using classic Anglo-Saxon terminology: in descending order of influence, king/queen, jarl, thegn, ceorl/freeman, and thrall.

King/Queen: These are the highest regional nobility, free from obligations to higher-ranking nobles but circumscribed by a web of customs and agreements with lesser lords and neighboring lands. Only one king or queen generally rules over a particular part of Ydra at a time, though rulership disputes have led to exceptions in the past, and the close relatives of royalty often enjoy special rights and obligations.

Several kings and queens exist within the borders of Ydra; some hold great influence, while others are little more than petty regional lords. The most influential is currently King Bor Snorrason of Kungesvald.

Jarl: This class consists of large hereditary landowners, sworn directly to the king or queen and sometimes rivaling royalty in power. Jarls are distinguished from the lesser classes primarily by the extent of their wealth and influence; they maintain their own networks of allegiances and sworn loyalties, and are usually capable of fielding small armies in their own right. The distinction between royalty and jarldom is essentially one of degree.

Thegn: This is a class of lesser nobility, exalted essentially by virtue of their association with a higher lord (or even a more powerful thegn). While thegns may receive substantial support from their patron, they are also bound by strict obligations of military service; therefore, they are primarily professional warriors. Thegns may or may not hold lands; if they do, a portion of the land's income is ceded to the thegn's patron. Thegns who do not own land often live and work with their lord, acting as that lord's agents and forming an elite bodyguard in wartime.

Ceorl/Freeman:Yddr society's closest equivalent to a middle class, this large group is made up of artisans, farmers, merchants, and other free workers. Members of this class may rent land from a more powerful landowner, or may hold it independently; in either case they must pay taxes to the nobles responsible for their protection. People of the ceorl class are free to bear arms, and most do. They make up the bulk of most armies in wartime, but generally earn most of their income from peaceful pursuits.

Thrall: Essentially slaves or bondsmen, these unfortunates are considered the property of a particular freeman or noble and are legally bound to obey that individual. Members of this class lack legal independence; any crimes they commit, for example, are their bondholder's responsibility. However, law and custom prohibit starving or cruelly abusing a thrall, and they may own money and possessions and work for their own benefit in their own time. They may not bear arms publicly. Members of other classes may legally become thralls through capture in wartime (if unransomed), by selling themselves into thralldom, or as a consequence of an unpayable debt; less legitimate means also exist.

Despite these social distinctions, Yddr culture does not partake of the rigid hierarchy common to later medieval society. Some nobles may prefer more formality and more hierarchy than others; freemen, likewise, may have widely varying opinions on their proper place in society relative to their nominal superiors. Especially in poorer and more rural regions, nobles may be more figures of mutual admiration than the recipients of divine ordination. Indeed, the titles above represent military power as much as purely social influence; jarl indicates warlord as much or more than it means peer of the realm.

Nonetheless, nobles (royals, jarls, and sometimes thegns) and their immediate relatives are often referred to as "lord" or "lady" by members of lesser classes. Depending on the situation, this may or may not be binding; some nobles insist on honorifics from those paying them tribute, while others do not. It is never binding upon people not paying tribute (directly or indirectly) to the noble they address, whether or not they are considered that noble's social inferiors; if the noble's status is obvious, however, omitting an honorific may be counted a deliberate snub.

Consequently, children of a ruling monarch are generally referred to as "lord" or "lady" instead of "prince" or "princess." Said children derive their honorifics purely from their association with the monarch; they gain no actual titles of nobility from the relationship, even if selected as their parents' heirs, and will not receive one until either their parent dies or they receive new lands or honors in their own right.

Social mobility is difficult and uncommon but not unheard of, especially for ambitious raiders or successful merchants. At the lowest ranks this is somewhat routine, as one may buy one's own way out of thralldom or be manumitted (dying bondholders, for example, often release exceptional servants as part of their last will); achieving noble rank, however, generally requires both money and acclamation.

Thegn-right is customarily granted by jarls or royalty to the heads of the wealthiest and most prominent households within their districts, provided they are able-bodied, in good legal standing, and capable of contributing soldiers in wartime; if the head of house is old, infirm, or unwarlike, the title may be bestowed upon one of their children. More rarely, an exceptional warrior may be given the rights of a thegn as a reward for heroism in battle, or for other services to their lord.

Achieving higher rank without inheritance is much rarer, as it implies a claim of local sovereignty and the ability to enforce it. A noble line may be snuffed out by feud or war or disease, or a weak heir may find their claim disputed; even in these cases, however, a claimant cannot hope to win the title without both a substantial personal fortune (to establish their worth and generosity, and to fund the inevitably ensuing warfare) and the acclaim and material support of many if not most important local families. Claiming noble title over another's lands, needless to say, is a serious affront, and can be expected to lead to a feud or duel if not a war.